Actually, I was just thinking about the same thing for a Suikoden I found with a cracked case. Anyway, I found that depending on what parts of the case are cracked, you may be able to just use parts from normal (audio cd size) jewel cases. The middle (black part) is really the only part that you can't get a replacement for in this way. The front and back of the multi-cd cases are all like the back part of normal cd cases, so you can just take them apart, get the inserts out, and use whatever pieces necessary to replace the parts that aren't in good shape. Worked great for me (although they are a little tighter and therefore a little harder to open...but they look much better). If you are a collector, you might not want to do this...but I'm pretty anal, and it looks good to me. Of course, you will need some cd cases, but they should be cheap, and easy to find.
[quote name='jimbodan']
also keep it mind, if the black part isn't broken you can just use the backs of any old cd jewel case to replace the fronts/backs of multi-disc cases.[/QUOTE]
I'm too slow...